The term "file units" is used herein to denote both file folders and card-like file guides that are inserted between groups of file folders to subdivide them for quick location of a desired file folder. The body of such a file unit, which is usually of pressboard or a similar cardboard-like material, is provided with a tab which projects from one of its edges and which carries identifying indicia. On file units used for drawer filing, the tab projects from a long edge of the body that will be uppermost in a drawer; on those used for shelf filing the tab projects from a shorter side edge. Where several tabbed units are installed in a bank of files, no tab should be directly in front of another, and therefore file units are usually made available in sets that have tabs at several different locations along their tabbed edges.
The type of file unit tab here under consideration is formed from one piece of thin sheet metal that is bent to a narrow U-shape to have a pair of flatwise opposing wings which overlie opposite surfaces of a file unit body and which are connected by a bight portion of the tab that defines a folded edge thereof. Adjacent to its folded edge each wing of the tab has a slot therethrough, and the slotted portion of the tab projects beyond the tabbed edge of a file unit body to which the tab is secured. A label or the like, inserted into the channel defined by this projecting portion of the tab, is visible through the slots. For its securement to a file unit body the tab is made with preformed eyelets in the portions of its wings that overlie the file unit body, the eyelets in one wing being formed as short, tubular rivets that can pass through punched holes in the body and be peened into engagement with the rims of the eyelets in the other wing.
Heretofore the securement of such metal tabs to file unit bodies has been accomplished mainly with manual operations. At one machine each body was punched with holes that were to receive the rivet eyelets of a metal tab. A tab was then manually preassembled to the body with its eyelets engaged in the punched holes, and the rivet eyelets were peened at another machine.
This procedure was obviously slow. The usual rate of production was on the order of six units per minute. In an effort to increase this production rate, a machine has heretofore been constructed that was intended to transfer tabs one-by-one from a storage location to a peening location where a previously punched file unit body was manually introduced between the wings of the tab and where a peening operation was then performed that secured the tab to the body. This machine did not operate successfully. Because the file unit bodies had been punched at another machine, problems arose with respect to bringing the file unit bodies to positions at which their holes were in accurate register with eyelets in a tab at the peening station. The mechanism for transferring tabs from the storage station to the peening station also gave rise to problems. That mechanism comprised a claw which engaged in the slot in one of the wings, and because of the thin metal of which such tabs are made, the claw was quickly abraded to the point where it could not accurately position the tabs at the peening station.
Considering the high degree of automation attained in the manufacture of more complex products, the amount of hand labor heretofore employed in file body tabbing suggests that a relatively low level of skill has been applied to the design of equipment for that operation. However, as exemplified by the difficulties encountered with the above discussed prior machine, the design of reliable apparatus for materially expediting the tabbing operation requires satisfactory solution of each of a number of problems, and it may well be that it is not so much lack of skill that has blocked the attainment of these solutions as the intractable nature of the problems themselves.
A major problem is that a satisfactory tabbing machine must be low in cost. To justify the investment in such a machine, it must displace a certain amount of hand labor. But the labor that it displaces is unskilled and therefore not well paid. Furthermore, sales volumes and selling prices also tend to impose economic limits o the value of a machine that will achieve a given rate of production.
For a tabbing machine to be inexpensive it must also be simple. Nevertheless, it must be very versatile, capable of tabbing file unit bodies of different shapes and sizes and of applying tabs of various shapes and sizes at various locations along the tab edges of such bodies; and it should be possible for relatively unskilled persons to adjust it quickly, easily and accurately to accommodate these several variables. Obviously, the machine should require an absolute minimum of maintenance and repair.
On the basis of economic considerations, complete automation of a file body tabbing machine does not seem to be justified. This means that file bodies will be manually fed into such a machine and removed from it. Since punching and peening operations present a high potential for serious injury, a tabbing machine must be so constructed and arranged that its operator cannot come into contact with its moving parts. From a safety standpoint it is also desirable that there be no electrical connections to the machine.
For manual infeed and withdrawal of file bodies to be fast, simple and efficient, there should be no need for the operator to devote special attention, or to exercise special skill, in accurate placement of the file bodies as they move into the machine, and the operator should not have to manipulate any control device that initiates or terminates an operation performed by the machine.
Fast and satisfactory operation of a tabbing machine requires that every file unit body be quickly and accurately brought into such relationship with a tab that a tab edge portion of the body is disposed between the tab wings. Although the wings of an unattached tab diverge slightly from its folded edge, the space between the wings is relatively narrow, and the file body must enter that space instead of passing to one side or the other of the tab, and as it does so its tab edge cannot be permitted to hang up on the rivet eyelets. Establishing the preassembled relationship is complicated by the thin, springy metal of which the tab is made and, to a greater extent, by the tendency for pressboard file unit bodies to warp markedly out of flatness, especially in damp weather.
A further consideration, which may be very important in some installations, is that a tabbing machine occupy a minimum of floor space.